Cisco LAN2LAN Software

Document ID: 15003

Contents

Introduction
Prerequisites
      Requirements
      Components Used
Symptom
Reason
Solution
IP
IPX
NetPro Discussion Forums - Featured Conversations
Related Information

Introduction

This situation occurs when an attempt is made to interoperate LAN²LAN with 3Com NetBuilder products when using IP and IPX via Frame Relay.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Symptom

The IP and IPX tables show all remote networks and routers. However, no file servers are visible and no traffic crosses the widearea link. A ping transmitted from the local side of the LAN²LAN does not reach the far side of the network. The local and WAN ports can both be pinged successfully. A reset of the 3Com router at a remote site solves the problem when the routing table is initially updated, but the entries quickly time out. Networks time out of the routing tables and the LAN²LAN broadcasts a "network unreachable" message (16hop RIP). The 3Com routers immediately respond with a RIP update for the network in question, but no traffic (IP or IPX) can cross the link.

Reason

The 3Com routers default to periodic RIP and SAP broadcast suppression in a format incompatible with the LAN²LAN.

Solution

The 3Com NetBuilders must be reconfigured to correctly enable RFC 1490 support for IPX and IP traffic over a Frame Relay network. Version 7.0 or later of the NetBuilder software is required.

IP

In the 3Com NetBuilder IP menu, use the ROUTES configuration option to define a static route for the remotely connected network. This is required because it appears that the 3Com router does not add entries to its routing table when it receives a RIP from the LAN²LAN. The LAN²LAN receives and understands the 3Com RIP without difficulty, so there is no need to configure static routes on the LAN²LAN.

The 3Com NetBuilder 7.0 software sets a static route in this format [all parameters appear to be required]:

B.B.B.B_M.M.M.M_G.G.G.G_T

(all IP addresses are entered in decimal) where:

B.B.B.B = Network address of the LAN you wish to reach
  M.M.M.M = Subnet mask for the LAN
  G.G.G.G = IP address of the WAN port on the LAN²LAN you wish to reach
  T       = Metric
  _       = [SPACE]

Once this is done, the IP services should be active and you should be able to PING and TELNET across the link with no difficulty. The 3Com router must be rebooted before the protocol comes into service if the MAC-layer address for the host router changes when the 3Com router is swapped out, as the NetBuilder does not attempt another ARP until rebooted. The default ARP timeout for the NetBuilder 7.0 software is 24 hours.

IPX

In the 3Com NetBuilder IPX menu, use the RIP configuration option to enable these three essential parameters:

WAN/NOWAN (this controls the 0x14 packet type broadcasts on WAN links)
  Periodic RIP Update Enable/Disable
  Periodic SAP Update Enable/Disable

Once all three of these are enabled, the IPX protocol settings on the 3Com router must be reconfigured. In the IPX menu, use the ADDRESS option to set the MAC-layer address of the remote router in the format:

%[MAC ADDRESS] @ [DLCI]

Once this is done, IPX traffic should begin to flow across the WAN link. There is no need to reboot for this change to take effect.

NetPro Discussion Forums - Featured Conversations

Related Information

• Technical Support & Documentation - Cisco Systems